Control device



March 2, 1954 w. c. ANDERSON 2,670,503

CONTROL DEVICE Filed April 30, 1949 2 Sheets-Sheet l IIJIIIIIIMH VEN I WILME .HN son 2 m2 ZZLZM ATTORNEY W. C. ANDERSON March 2, 1954 CONTROL DEVICE 2 Sheets-Sheet 2 Filed April 30, 1949 INVENTOR WILMER CHNDERSON $012; ATTO R N EY Patented Mar. 2, 1954 UNITED STATES PATENT OFFICE CONTROL DEVICE Wilmer C. Anderson, Greenwich, Conn., assignor to Deering Milliken Research Trust, Greenwich, Conn., a nonprofit trust of Maine Application April 30, 1949, Serial No. 90,651

15 Claims. 1

The present invention relates to control of textile operations and comprises a novel device, which, while particularly adapted for monitoring drafting or gilling machines of the type used in processing worsted sliver, may be advantageously employed with other types of textile processing machines, for example carding machines.

In yarn manufacture, there are a number of operations prior to long draft roving operations in which sliver is condensed from a web, or sliver is doubled and drafted. Variations in weight per unit length of the sliver produced in any of these operations result in corresponding but greater variations in the diameter of the roving. When the roving is not uniform, uneven yarn results with corresponding waste of material, time and labor. In order to minimize variations in sliver, various devices which measure the weight or thickness of the sliver as it emerges from a processing mechanism and which operate to change the rate of emission of the sliver in response to such measurement, have heretofore been suggested. Such devices, however, can only afiect succeeding portions of the sliver. Moreover, such devices, contrary to their intended purpose, tend to accentuate rather than to minimize or suppress the unwanted variations in the sliver. That this is the effect of such attempts to control the rate of delivery of the sliver will be readily appreciated from a consideration of what occurs, for example, during drafting of fibers in a pin drafter. In such a machine, the combined stock of gilled sliver from the can or ball creel is engaged by the intersecting pins of the faller bars which move forward at a rate less than that of the periphery of the draft rolls, the pins exerting a drawing action on the relatively slowly moving incoming stock and a holding action on the relatively rapidly moving outgoing stock.

For various reasons, for example because of bent or faulty pins, an excess of fibers at one moment may be held back by the pins with the result that the'sliver emitted by the draft rolls is excessively light at that moment. As the pins advance these excess fibers are suddenly released from the pins and approach the draft rolls together, drawing other fibers with them and thus resulting in excessively heavy sliver followed by another light section of sliver; Thus, once uneven drafting occurs, sliver is produced in which lengths that are too heavy alternate with lengths that are too light and a device which automatically increases the draft when the emitted sliver is too heavy accentuates the lightness of the succeeding length of sliver. In other words, when the weight ofemitted sliver departs too far from that desired, correction cannot be made by change of .draft. The. machineshould be stopped for adjustment or repair. The same is true of carding or combing machines.

It is an object of the present invention, therefore, to provide a monitoring device for a sliver processing mechanism that will detect excessive variations in weight of emitted sliver and will operate to shut down the machine when the sliver is either too light or too heavy.

It is a further object of the invention to provide a device of the above character that will permit of ready adjustment of the permissible variations in weight of the sliver emitted by the machine being monitored.

It is also an object of the invention to provide a monitoring device that will detect a given percentage change in weight of emitted sliver, thus requiring substantially no readjustment when sliver of diiferent average weight is to be processed.

These and other objects of the invention are attained in accordance with the invention, by the provision of a sturdy compact device adapted to be mounted on, or adjacent to, the machine to be monitored and circuit means connected thereto and to the energizing and control circuit of the machine. The device includes a pivoted feeler which lightly contacts the emitted sliver during passage of the sliver through a condensing trumpet or channel and which is arranged to initiate stopping of the machine when the depth of the sliver in the channel departs too widely from a predetermined value. Stopping of the machine is initiated when a rockable contact carrying member engages either of a fixed pair of contacts adjustably positioned at opposite sides of the member. This rockable member could itself be the pivoted feeler, but in the preferred embodiment of the invention the rockable member is a separate element and is coupled to the feeler so as to be moved thereby. The coupling permits of ready adjustment of the extent of angular displacement of the member for a given angular displacement of the feeler and avoids the necessity for readjusting the spacing of the fixed contacts when sliver of a different average weight is being processed by the machine. This and other features of the invention and of the preferred embodiment thereof will become apparent as the description proceeds.

Of the accompanying drawings, Fig. 1 is a perspective view of the mechanical components of a monitor device representing a specific embodiment of the invention, the casing and part of the adjusting means being omitted for the sake of clarity;

Fig. 2 is a front elevation, partly in section of the device of Fig. 1 and including the parts omitted therefrom;

Fig. 3 is a vertical sectional view taken on th line 3-3 of Fig. 2; I

Fig. 4 is a rear elevation of the device of Fig. 2 but with the cover removed;

frommaximum to minimum level.

Fig. 5 is a perspective view showing the device of Figs. 1 to 4 mounted between the delivery rolls of a drafting mechanism to be monitored and the coiling can of the machine; and

Fig. 6 is a circuit diagram of the device.

In the particular embodiment of the invention illustrated in the drawings, the mechanical parts of the device, as shown in Figs; l'to 5 inclusive, include a base member 2. which has. formed therein a smooth walled channel 4 for passage of sliver therethrough, a feeler 5 which is pivotally mounted above the channel and yieldingly engages the sliver, indicated at S in. Figs. 3 and 5, and a pivoted contact arm 8 coupled to the upper end of the feeler i5 and adapted to be moved thereby. The base 2 may be, and preferably is, a brass casting from a mold, the casting being thoroughly buiied at least along the wall of the channel 4. The channel 4 is preferably shaped, as shown best in Fig. l, to provide an entering condensing section 4a for the sliver, in which the width of the channel gradually decreases from a relatively wide mouth at the rear of the device to a relatively narrow neck I substantially midway of the length of the channel, a measuring section 4b forward of the neck ID, in which the side walls are substantially parallel and the channel width is substantially greater than that at the neck Iii, and an exit portion 40 for the sliver in which the width gradually decreases up to the point of emergence of the sliver from the channel, at which point the width is substantially equal to that at the neck-[IL If desired the base 2 may be formed With a forwardly extending shelf i2 provided with an aperture l4 through which the emerging sliver may be fed and directed to collecting means, such a a sliver coiler can, the casing l of which is indicated in part in Figs. 2 to 5.

Secured to opposite sides of the base 2, as by bolts [6, are side walls is which extend to a level above that of the base and support a plate member 20 which is preferably hingedly connected to one side Wall [8, as by a hinge 22, and releasably latched to the other by a fastener 24. A rear wall 26, Which is secured to the plate 26, as by screws 21, is cut away adjacent the entrance to portion to of the channel as indicated at 26a in Figs. 3 and 4, to provide a relatively shallow inlet passage for the sliver. Preferably, as shown in Fig. 3, the wall 25 at the boundary of the opening 26a is rounded and polished to insure that the sliver will be engaged only by smooth surfaces in its passage through the device. The plate 20 has an aperture therethrough .gear3l which meshes with th teeth of a large gear. heel 33. The wheel 33, which has indicia purpose hereinafter described, is fixed to a shaft 35 suitably journalled in a bushing 37 in the plate 20 so as to be free to rotate when the bolt 39 is turned. 'The gear ratio between gear 3|, and wheel 33 is such that the wheel makes about one revolution when the bracket 32 is moved Il 1 e bracket 32 isformedjwith a forwardfex tension'32a which is provided with a tran'sverse passage therethrough for reception'ofone end of a pivot pin 34 for the feeler 6. The other end of pin 31; i iournalled in a. bearing 36 which is fricti nal mounted in anapcrture in a st p 3 The strip 321) is secured to the bracket 32, as by screws 38, and is so spaced from the extension 32c as to accommodate the feeler 6 therebetween. The feeler 6 comprises a strip of sheet metal which is bent through a right angle near the-midsectio.n; of its length and bent into the form of a U at the sliver engaging end. The pivot pin 34is welded or otherwise rigidly secured to the feeler above the right angle bend therein. A collar 49 is fixed to the bearing 35 between the-pin 34 and the inner wall of strip 32b and a light spiral spring 42, is coiled about this collar. One end of the spring 42 is secured to the collar 9 and its other end is secured to a short pin 44, which is welded to the feeler 6 below the pivot pin 34. The outer end of the bearing 36 has a head thereon provided with a cross cut or groove for reception of a screw driver or the like to permit the tension of the sprin 42 to .be. readily adjusted. The. spring 42 biases the feeler and insures continued light contact of the Li -shaped end thereof with the sliver in the portion 412 of the channel. A pair of ui pins 45, which are fixedly secured to the late 20 and extend vertically downward there= from and through suitable guide passages in the bracket 32, prevent turning of the bracket when the bolt 33 isv turned to adjust the level of the bracket and of the, ,feeler'carried thereby.

The plate 23 isprovidecl with a relatively wide slot 45 above, the pin 34 to, accommodate the pp r end. f the feeler and to provid sufii ien clearance for oscillation of the feeler about the axis of the pin in response to variation in the thickness. of the sliver.

Adjacent the opening 46 in the platen there is a groove 48 which is disposed parallel to the pin as and, in this groove is a pin 50 upon which is oscillatably mounted. the contact arm 8, the pin 59 being held in the groove 48 by means of .a shaft lock indicated at 52. The arm 8 is preferably made of iron or the like material of high magnetic permeability and a small magnet in the form of a rod 54, is secured to the feeler 6 ab ve the. plate 2%. and. on the side of the feeler dja nt. the contact arm. so as to magn t lly and detachably couple the feeler and contact arm together.

Mounted on the plate 20, as by an angle piece 5 is. ulat n strip 53 carryin a c ndu tin bracket to having a pair of spaced horizontally p j t n a ms 62-, T e a ms 62 extend on onposite sides of the contact 8a carried by the arm 8 and each carries a contact tipped screw 64 in the path of movement of contact 8a.

A conductor 66 electrically connects the bracket to the terminal of a socket 68 mounted on the plate 29, No electrical connection to the e m 8 e u ed as it may e grounded through the device and the machine upon which the device is mounted as will be described in connectionwith Fig, The various parts carried by the plate 20 are enclosed within a removable cover 10 which is suitably apertured to permit the knurled head 39a of the screw 39 to extend therethrough, is cut away to accommodate an, external lead its and plug M and is also cut away to clear a o r ar d 19 n tt d Win s-i i i i' ii -h sore? iebcvckthl ra m -8 iriorder that the positi -91? the eunder!! m y viewed Adjustment'of the above described device, to respond to a given percentage variation in sliver thickness, may be effected as follows. A gauge, such as a rod or the like, of a thickness equal approximately to the thickness of a sliver of weight intermediate the heaviest and lightest expected to be handled by the device, is inserted in the channel 4 under the feeler. The knob 30a is then turned to raise or lower the bracket 32, as the case may be, until the arm 8 is vertical. The gauge is then removed from the channel and a second similar gauge the thickness of which is less than that of the first by the desired percentage, say percent, is inserted in the channel. The feeler and contact arm will then turn on their respective axes (counterclockwise as viewed in Fig. 3). With the cover it removed, that one of the fixed contacts 84 which is thus approached by contact 8a is then adjusted either toward or away from contact 8a until good but light contact is made between these contacts while the feeler is in engagement with the gauge, the tension of spring 42 being increased, if necessary, to insure that the feeler maintains contact with the gauge. tact 64 is then adjusted in the same manner, this time with a gauge the thickness of which exceeds that of the first gauge by the given percentage. After these adjustments are completed the cover 10 may be replaced as the device is ready to monitor any sliver Within the range of weights to be handled, to detect percentage variations equal or exceeding that for which the contacts have been adjusted. When initially placed in operation to'monitor a sliver of a definite average weight per unit length, the bracket 32 is raised or lowered by turning the bolt until the end of the arm 5! is midway the contacts 64, as viewed through the window l6, when a sample of sliver of such average weight is placed in, or passed through, the channel 4. The indicia on the segment of wheel protruding through the cover, being necessarily correlated with the level of the bracket 32, provide assistance to the operator in this adjustby the magnetic pin 54, undue pressure of the contact 8a against a fixed contact such as would occur when a section of sliver of excessive thickness engages the feeler is avoided. After separation of the feeler and contact arm as a result of the passage of such excessively thick sliver through the device, the feeler and arm will automatically be recoupled under the influence of spring 42 when the thickness of the sliver returns to its normal range.

The control circuit actuated as a result of a engagement of contact 8a with either of contacts 64 is shown in Fig. 6 to which reference may now be had.

In Fig. 6, the reference numeral H indicates the drive motor of a sliver processing machine,

for example a pin drafter the draft rolls [8 of which are indicated in Fig. 5. Power supply lines for the motor 1! are indicated at 18. A normally energized relay 80, over front contacts, controls the circuit of motor 11. Relay 80. is connected The position of the other conthrough normally closed front contacts of a sec;- ond normally energized relay 82 across the secondary of a step down transformer 84, the primary of which is connected across the ungrounded power lines 19.

The energizing circuit of relay '82 includes its own front contacts, back contacts of a normally deenergized safety relay 86, and front contact 81 and armature 88 of a relay 89 in the anode circuit of a triode 90. Triode is energized except when the contact carried by arm 8 of the monitor engages one or the other of fixed contacts B4. The energizing circuit for triode 90 includes a transformer 92 the primary of which is connected across the secondary of transformer 84 through a double throw switch Sw, which, when the monitor is in operation, is closed in the position shown in the drawing. One end of the secondary of transformer 92 is connected to the anode of tube 90 through the winding of relay 89 and the other end is connected through normally closed contacts of a start button 94 and series resistors 96, 88 and I00 to the cathode of tube 80. An intermediate point on the secondary of transformer 92 is connected to the junction of resistors 98 and I00 and, through a resistor I02, with the control grid of tube 90. The junction between resistors 98 and 98 is connected to the mechanism being monitored, indicated as ground G and to a back contact I04 associated with a second armature I05 controlled by relay 89. Contacts 64 of the monitor are connected together, as heretofore described and, through lead I06, are connected to the control grid of tube 90 and to the armature I05. Thus, when the contact carried by arm 8 is not in engagement with either contact 64, the grid of tube 90 is at a potential sufficiently above that of the cathode to insure energization of tube 90 and consequently of relay 89 as well. Arm '8 is grounded through the mechanism being controlled, indicated as ground G in Fig. 6, and hence, when the contact carried by arm 8 engages either of contacts 64, the potential of the grid will be brought below that of the cathode and tube 90 will be cut off. Relay 89 thereupon drops its armatures to open the circuit of relay 82 and to maintain tube 90 deenergized by connecting the control grid over back contact I04 to ground and to the junction of resistors 96 and 88. Deenergization of relay 82 opens the circuit of relay 80, which in turn drops its contacts to open the circuit of the motor I1. When relay 89 drops its contacts the circuit for a signal light R is closed over a back contact associated with armature 88. The circuit for the lamp thus closed includes a third blade of switch Sw which is connected to the to that to which armature 88 is connected.

Lighting of lamp R thus indicates that the stoppage of the mechanism was caused by operation of the sliver monitor, and not because of some other stop motion device that may be associated with the machine. Such other devices may, and preferably do, control relay 86, causing energization thereof when the machine is to be stopped because of overload or the like. Textile machines are ordinarily equipped with a number of such stop motion devices and as these other devices form no part of the present invention they are not specifically illustrated in the drawing. Normally open contacts I08 in the circuit of relay 88 may be taken as a symbolic representation of such other devices.

After the motor 11 has been stopped, either as a result. or operation. oi: the sliver;-monitor.-; as above described, or as a result of-operation of another stop motion device of the mach neri can be started by he depression oi he, ar button 94, which closes apiclgup circuit'for relay 82 and pens the connection betw en the end f the secondary of. transformer 22: and resi tor 95 in the. cathode circuit of tube 9.0- Th penin of this connection removes the bias on. he control grid and ermits energization of tube 90. and consequent completion of the holdin c r uit. of relay 82. With return of. the. start button to normal position, tube 9.0 will. remainenergi e provided neither contact 64 is grounded through the arm 8., that is, provided the sliver thickness is within the desired range. It the thickness or the sliver is not within the desired range, 'tube at will be deenergized as. soon, as the start button is released and accordingly relays 39, 82; and; so will againv release their contacts and motor 1.1 will be deener iz d.

If it is desired to discontinuethev control, by the monitor without interfering with the control of the motor I! by the other stop motiondevices, the switch Sw is thrown to the left, as viewed in Fig. 6, in which position the circuit of the primary of transformer 9.2 is opened and the holding circuit of relay &2. is completed through a blade I09 of: the switch Deenergization of: the transformer 92 extinguishes a signal lamp H which,v when the monitor is functioning, is energ-ized from a separate secondary winding of this transformer.

One specific embodiment of the. monitor, together with a specific control oircuitresponsive thereto, have now been described. Obviously various changes in the specific oonstructionand in the specific circuit could be made without departing from the spirit of the invention or the scope of the accompanying claims. For example, the contact arm and feeler could be coupled by other than magnetic means or the feeler itself could be the contact. arm. In the latter case the contacts, either the movable or the fixed, should of course, be sufilciently elongated to insure contact. closure at any level of the pivotal axis of the-feeler. Other modifications will occur to those skilled in the art.v

The following is claimed:

'1. A monitor for a sliver processing machine comprising the combination with a fixed memher having a channel therein for passage of sliver therethrough of means responsive to the depth of sliver in said channelrand means controlled by said last mentioned means for ste ping the, sliver processing machine upon a given change in depth of sliver in said channel, said responsive means including a feeler pivotally mounted above the channel and biased into ongagement with the sliver so as to have its angular position depend upon the depth of sliver in the channel and means for adjusting thespacving between the'feeler mounting and the channel.

. 2. A monitor for a sliver processing-'machine comprising the combination with a first'imcmber having a channel therein" for'pass'age of sliver therethrough of means responsive to. the depth of sliver in said channel, said responsive means comprising. a' feeler pivotally mounted above the channel and biased into ongagement with the sliver so as to have its angular position depend upon the...depth. of slivcrin the: channel; a contact arm pivotally mounted above the channel and coupled to said'feeler so as to. be. roolrcd thereby 'uponchange in depth or the sliver the chann l, c ntacts p it;ion d at opposite sides of saidcontactarm for en easement therewith when the arm is rocked in either direction through a predetermined angle, means for adjusting the spacing between the piv otal axes, of the feeler and contact arm for varying the extent of angular movement of the arm for a given angular movement of the feeler, and means responsive to engagement of said arm with either contact for stopping the sliver processing machine.

3. The monitor according to claim 2 wherein said contact arm is pivotally mounted at a fixed distance. above said channel and wherein said adjusting means adjusts the level of the pivotal axis of the feeler, whereby when sliver of a different average thickness is; processed by the machine and the level of the axis of the feeler correspondingly adjusted, a given angular displacement of the contact arm corresponds to the same percentage variation in depth of sliver in the channel.

4. The combination with a sliver processing machine having driving means of a monitor comprising a base member having a channel therein for passage of sliver therethrough, a feeler, means for pivotally supporting said feeler above said base. member with a part of the feeler in engagement with sliver in said channel, whereby change in the depth of; the sliver in the channel rocks said ieeler on its pivot, means responsive to a predetermined angular displacement of said feeler on its pivot, indicative of a predetermined change in depth of the sliver in the channel, for stopping the driving means of the sliver processing machine, and means for adjusting said feeler supporting means toward and away from said base member.

5. The combination according to claim 4 wherein said responsive means includes a rockable contact arm, a fixed contact positioned for engagement with the arm upon predetermined angular displacement thereof in one direction, a second fixed contact. positioned for engagement with said arm upon predetermined angular displacement thereof in the other direction, and means coupling said feeler to said arm for movement therewith.

6. The combination according to claim 5 including a support for said contacts fixedly positioned with respect to said base member, said arm being pivotally mounted on said support and said ieeler supporting means being carried by and adjustablyspaced from said support.

'7. A monitor for sliver processing machines comprising a base having a channel formed in the upper surface thereof for passage of sliver therethrough, said channel being shaped to provide an entrance section in which the side walls converge for condensing sliver entering therein, an intermediate measuring section in which the side walls are substantially parallel and a sliver discharge section, av framework carried bysaid base and including a plate horizontally disposed above said channel and; spaced therefrom, a

bracket disposed: between said plate and said base, support means for said bracket mounted on said plate, a generally vertically disposed feeler pivotally mounted on said bracket" for movement about a horizontal axis, the lower end of said feeler being disposed above the measurjust-mg the. level or said bracket with" respect. to

9 said base, and means carried by said plate an responsive to predetermined angular displacement in either direction of the feeler about its pivotal axis for initiating stoppage of a processing machine.

8. The monitor according to claim 7 wherein said last mentioned means includes an arm pivotally mounted on said plate for oscillation about an axis parallel to the pivotal axis of said feeler and means coupling said arm and feeler together.

9. A stop motion device for a sliver processing machine comprising in combination a feeler pivotally mounted above the path of travel of sliver processed by the machine and having a part thereof disposed for continuous engagement with sliver passing thereunder, and meats controlled by said feeler and responsive to angular movement thereof in either direction through a predetermined are for stopping the machine, said last mentioned means including a pivotally mounted contact arm releasably coupled to said feeler, contacts spaced from said arm for engagement therewith upon predetermined displacement thereof in response to pivotal movement of said feeler, and means for adjusting the distance between the pivotal axes of the feeler and contact arm.

10. The combination with a sliver processing machine having an electric driving motor and energizing circuit therefor of a monitor for initiating opening of said circuit upon predetermined percentage variation in the volume of sliver emitted from the machine per unit time, said monitor including a member positioned adjacent the output end of the machine and formed with a channel having a fixed bottom wall for passage of sliver thereover and fixed side walls for passage of sliver therebetween whereby the depth of sliver in the channel will vary with the vol I ume of sliver being emitted from the machine per unit time, a feeler pivotally mounted over said channel and for engagement with the sliver, a pair of fixed contacts and a contact adapted to be moved by said feeler into engagement with either of said fixed contacts, and circuit means including said contacts and responsive to engagement of said movable contact with either of said fixed contacts for opening the circuit of said motor.

11. The combination according to claim 10 wherein said circuit means includes a relay, means responsive to deenergization of said relay for opening the circuit of said motor, a second relay, a holding circuit for aid first relay including contacts controlled by said second relay, a normally energized electronic tube having a control grid, cathode and anode, said second relay being connected to said anode for energization when said tube is energized, an energizing circuit for said tube, and circuit connections including said cathode, grid, fixed contacts and movable contact for biasing said grid to cut off energization of said tube upon engagement of said movable contact with either of said fixed contacts.

12. The combination according to claim 10 wherein said circuit means include a normally energized electronic tube having a control grid, cathode and anode, a relay connected to said anode for energization when said tube is energized, said fixed contacts being connected with said control grid and said movable contact being grounded through the machine, an energizing circuit for said tube grounded through the machine at a point the potential of which is lower than that of the cathode when the tube is passing current, the grid of said tube being connected to said energizing circuit at a point the potential of which is above ground, whereby engagement of said movable contact with either of said fixed contacts biases the grid of said tube to cut oii energization of said tube to cause deenergization of said relay, and means responsive to deenergization of said relay for opening the circuit of said motor.

13. The combination with a sliver processing machine having driving means of a monitor comprising a base member having a channel therein for passage of sliver therethrough, a feeler, means for pivotally supporting said feeler above said base member with a part of the feeler in engagement with sliver in said channel, whereby change in the depth of the sliver in the channel rocks said feeler on its pivot, means responsive to a predetermined angular displacement of said feeler on its pivot, indicative of a predetermined change in depth of the sliver in the channel, for stopping the driving means of the sliver processing machine, said last mentioned means including a rockable contact arm, a fixed contact positioned for engagement with the arm upon predetermined angular displacement thereof in one direction, a second fixed contact positioned for engagement with said arm upon predetermined angular displacement thereof in the other direction, and means magnetically coupling said feeler to said arm for movement therewith while permitting automatic detachment upon passage of excessively thick sliver through said channel.

14. A monitor for a sliver processing machine comprising the combination with a fixed member having a channel therein for passage of sliver therethrough of a feeler operative from different set positions with respect to said channel, means biasing said feeler into engagement with the sliver, said feeler being movable in response to variations in thickness of the sliver passing through said channel, means actuated by said feeler for stopping said machine upon a given change of sliver thickness in said channel including a stop control member operative for normally inoperative position corresponding to the desired thickness of sliver being processed to either of two operating positions corresponding to a predetermined change in sliver thickness respectively greater or less than said desired thickness, and means for adjusting the operative position of said feeler toward and away from said channel to accommodate the processing of sliver of different average thickness.

15. The sliver monitor according to claim 14 wherein said stop control member coacts with adjustable means for determining the two operative positions of said member.

WILMER C. ANDERSON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 221,159 Dawson Nov. 4, 1879 1,791,289 Scott Feb. 3, 1931 1,899,791 Brennen Feb. 28, 1933 2,270,720 Thompson Jan. 20, 1942 2,390,799 Linsenmeyer et al. Dec. 11, 1945 2,400,837 Nesterowicz May 21, 1946 2,412,324 Crum Dec. 10, 1946 2,433,444 Eichinger Dec. 30, 1947 

